The proposed research deals with the synthesis and physicochemical study of monomeric homo- and heterometallic binuclear transition metal complexes, suitable for study of electron-transfer between metal sites, and metal complexes of molecular oxygen. Ligand systems of the essential Schiff base type will be employed in each case. Binuclear complexes will be of types which allow the preparation of mixed valence species and examination of electron delocalization, electron exchange rates between metal centers, redox potentials, and their dependence on metal-metal distance, coordination geometry, and nature of the intervening ligand structure between metal centers. Results from this research are of potential value in elucidating electron transfer phenomena in metal-containing biological systems. The proposed preparation of stable dioxygen complexes (containing the unit M-O2, M equals Co,Fe) will involve the use of ligand systems whose structures sterically prevent attack of bound oxygen by a nucleophilic metal center, and thus represents an approach to the synthesis of species having the properties of the active site of hemoglobin or myoglobin but without the protein. Isolation of these oxygen adducts will allow x-ray structural determination of the mode of M-O2 binding, and investigation of the electronic features of this unit and reaction of bound oxygen with oxidizable substrates.